1. Field of the Invention
This invention relates to a positive crankcase ventilation system for use in an internal combustion engine and, in particular, to a device for thermal management of the positive crankcase ventilation system.
2. Disclosure of Related Art
Conventional gasoline and diesel internal combustion engines often employ a positive crankcase ventilation (PCV) system. During the final stages of combustion in the engine, gaseous mixtures of unburned fuel, air, and other constituent products of combustion often leak past piston rings disposed within the engine""s cylinders. These gaseous mixtures, commonly referred to as xe2x80x9cblowby-gases,xe2x80x9d will interfere with engine performance if allowed to remain within the crankcase. The blow-by-gases include toxic byproducts of the combustion process, however, and it is therefore undesirable to vent the gases directly into the atmosphere. The PCV system employs an engine vacuum to draw blow-by-gases into the engine intake manifold for reburning in the combustion chambers and controls the flow of the blow-by-gases.
Among other constituent elements, blow-by-gases contain high levels of water vapor. During a variety of operating conditions this water vapor can freeze, forming snow and ice within the PCV system, including the PCV valve, ventilation lines, and other locations. Freezing can occur, for example, when the vehicle engine is started from a cold start in low ambient temperatures (e.g. less than 35xc2x0 F) or as a result of the effects of wind chill during motion of the vehicle, which can affect the vapor lines exposed to the ambient environment. In the latter case, freezing in the PCV system has been found to occur even at relatively high ambient temperatures when the vehicle is traveling at a relatively high rate of speed with little load on the engine, for example, when the vehicle coasts or idles down an incline. Frozen accumulations in the PCV system can cause catastrophic failures of the engine, such as engine oil blow outs, crankcase seal blow outs, or throttle sticking, all of which have the potential to endanger the driver and vehicle occupants.
Various solutions have been proposed in the prior art to prevent the freezing of PCV systems. In U.S. Pat. No. 4,768,493 a system is disclosed in which a water jacket circulates warmed engine coolant around the PCV valve. However, this system and other systems employing engine coolant have several disadvantages. The systems are slow to work during a cold start and fail to provide heat quickly enough to prevent freezing. In addition, these systems remove capacity and related efficiency from the engine cooling system, which is generally carefully designed for the engine. Finally, these systems are relatively expensive and complex and add unnecessary weight to the vehicle. In U.S. Pat. Nos. 5,970,962 and 6,062,206 electric heaters are disclosed for heating the PCV system. Electric heaters, however, drain power from the electrical system of the vehicle. The heaters are also relatively expensive and labor-intensive with respect to manufacture and installation. In addition, the above-identified solutions and other solutions are not completely effective in overcoming the effects of wind chill which vary widely responsive to factors such as ambient temperature, the moisture content of the environment, and the velocity of the air surrounding the PCV system.
Thus, there is a need for a more effective thermal management device for a PCV system that will minimize or eliminate one or more of the above-mentioned deficiencies.
The present invention provides a thermal management device for a PCV system of an engine including, but not limited to a vehicle engine.
A thermal management device for a PCV system of an engine in accordance with the present invention includes a heat pipe having first and second ends. One end of the heat pipe is configured for connection to a heat source. The heat source may, for example, comprise a cylinder head of an internal combustion engine. The heat pipe is further configured to be in thermal contact with one or more components of the PCV system. For example, the heat pipe may be in thermal contact with a PCV valve or a hose coupled to the PCV valve. In accordance with the present invention, the phrase xe2x80x9cthermal contactxe2x80x9d includes placement sufficient to permit thermal conduction, convection, and/or radiation.
The present invention also provides a PCV subassembly for assembly with an engine. The subassembly includes a PCV valve and a heat pipe. One end of the heat pipe is configured for connection to a heat source in the engine and the heat pipe is configured to be in thermal contact with the PCV valve.
A thermal management device in accordance with the present invention has several advantages as compared to conventional devices for regulating temperatures within PCV systems. First, the inventive system device works quickly, as heat pipes can rapidly transfer heat. Additionally, the inventive system requires no external energy to operate it only requires a temperature difference to be operational, such temperature differences being readily available within an engine system. The inventive system also does not cause parasitic losses in the automobile electrical system or engine coolant system. Finally, the inventive system is also capable of preventing freezing of the PCV system in widely varying conditions.
These and other features and objects of this invention will become apparent to one skilled in the art from the following detailed description and the accompanying drawings illustrating features of this invention by way of example.